Laboratoire Interdisciplinaire Carnot de Bourgogne UMR 5209 CNRS / Université de Bourgogne. 9, Av. A. Savary, BP F21078 Dijon, France,

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1 SPARK PLASMA REACTIVE SINTERING: A SOLUTION FOR PRODUCING DENSE MATERIALS Frédéric BERNARD Laboratoire Interdisciplinaire Carnot de Bourgogne UMR 5209 CNRS / Université de Bourgogne. 9, Av. A. Savary, BP F21078 Dijon, France,

2 CONTENTS : REACTIVE SINTERING I. INTRODUCTION II. PREPARATION OF REACTANT POWDER MIXTURES III. DEVELOPPEMENT OF SPECIFIC TOOLS IV. EXAMPLE 1 : SHS REACTION IN Mo/2Si SYSTEM V. EXAMPLE 2 : SOLID STATE REACTION IN IODOAPATITE VI. SOME APPLICATIONS

3 Process B (10 µm) A (40 µm) Many chemical transformations are possible : Balls Mixture of powders Amorphous phases, Allotropic and order/desorder transformations Metastable materials, non-equilibrium structures, nanomaterials A + B = n(ab)

4 Comminution, Mechanical Activation and Mechanical Alloying Fe+Al c) mm mm mm mm mm mm 600µm

5 Repeated Fracture-cold cold welding process during high energy ball-milling Case 1 : Ductile mixture Case 2 :Brittle mixture C.Suryanarayana. Progess in Mater. Sci. 46 (2001) 1

6 Ball milling of Al with AlN (brittle phase) Al particles = pseudo-spherical shape Ball milling of Al without AlN (brittle phase) Al particles = lamellar shape C.Goujon et al. Powder Techn. 105 (1999) 328

7 1 : Ductile-Ductile mixture A B Ductile behavior E.Gaffet et al. et al. J.Mater.Chem 9 (1999) 305 Nb/Al system V. Gauthier et al. Mater. Sci. Eng. A265 (1999) 117

8 SEM micrographs: Cu-37%at. Al powders produced after (a)-1h and (b)-2h respectively Bright layers = Cu; Dark kayer = Al D.L.Zhang et al. Mater.Sci.Eng. A301(2001) 90. SEM micrographsdepicting the convoluted lamellar structure obtained during milling of Ag/Cu C.Suryanarayana. Progess in Mater. Sci. 46 (2001) 1

9 Repeated Fracture - cold welding process Turbula Mixture (4h) Al Fe Fe Al intensité (u.a.) µm FeAl 100 Al 111 Al Fe 110 FeAl 110 MA mixture: Fe + Al during 4h No FeAl intermetallics compounds observed FeAl 111 Al Fe 200 FeAl 200 FeAl 210 Al 311 Al Fe 211 FeAl 211 Al Fe 220 FeAl µm Micrometric Nanostructured Aggregates Fe+Al Grain of MA powder: Nanocristallytes of m Fe (70 nm) and Al (90 nm) [BET, MEB] [Analyse de profils DRX] theta ( )

10 CONTROL OF THE HOMOGENEITY IN CHEMICAL COMPOSITION 300 µm 300 µm C Fe Fe B C A A B C B C Al 4 µ m 10µ m A Al C Fe Fe Fe (a) (b) (c)

11 2 : Brittle - Ductile mixture Dispersion of Er 2 O 3 particles in a mechanically milled α Ti alluminum alloy matrix C.Suryanarayana. Progess in Mater. Sci. 46 (2001) 1

12 3 : Brittle - Brittle mixture The harder Si Particles are incorporated in a softer Ge matrix after mechanically alloying the Si-Ge powder mix for 12h. Si-Ge : R.M. Davis et al. Scripta Metall. 21 (1987) 305 Mn-Bi : R.M. Davis et al. Metall. Trans. A19 (1988) 2867

13 - Grain size heterogeneity! - Oxide dispersion heterogeneity! - Local chemical composition! - many structural defects as dislocations, twins! - defects distribution! --!!!

14 Mechanically activated mixture (Mo/Si) characteristics Succession of fracture / welding Si Ω = 350 rpm, ω = -250 rpm, t = 2 h Mo intensite (coups) φ Mo = 50 ± Mo 0, Si nm P4(350/-250/2 et φ Si =20 h) ± 0,31 nm Mo Si (111) XRD : Whole pattern fitting LeBail method (110) (220) Th Degrees (311) (200) Mo 0.00 % Si 0.00 % MA mixture : without intermetallic compound (400) (211) (331) Mo + 2 Si agglomerates micrometric nanostructured : µ(nmo + 2 nsi) Powder MA: Nanocrystallites de µm Mo (50 nm) et de Si (20 nm) [BET, SEM] [XRD profile analysis] with µ = micrometric grain and n = nanostructure

15 SEM-EDX EDX ANALYSIS

16 CONTROL OF THE HOMOGENEITY IN CHEMICAL COMPOSITION

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